Solid-state imaging device and method for manufacturing the same

ABSTRACT

The present technology relates to a solid-state imaging device capable of reducing bonding defects when two substrates are bonded to each other, and a method for manufacturing the solid-state imaging device. The present technology provides a solid-state imaging device that includes: a first substrate including a first electrode formed with a metal; and a second substrate that is a substrate bonded to the first substrate, the second substrate including a second electrode formed with a metal, the second electrode being bonded to the first electrode. In at least one of the first substrate or the second substrate, a diffusion preventing layer of the metal is formed for a layer formed with the metal filling a hole portion, the metal forming the electrodes. The present technology can be applied to solid-state imaging devices, such as CMOS image sensors, for example.

TECHNICAL FIELD

The present technology relates to a solid-state imaging device and amethod for manufacturing the solid-state imaging device, and moreparticularly, to a solid-state imaging device capable of reducingbonding defects when two substrates are bonded to each other, and amethod for manufacturing the solid-state imaging device.

BACKGROUND ART

Higher integration of semiconductor devices of two-dimensionalstructures has been realized through introduction of fine processing andenhancement of packaging density. However, there are physicallimitations to higher integration of two-dimensional structures by thesemethods. Therefore, to further reduce the sizes of semiconductor devicesand increase the pixel density, semiconductor devices havingthree-dimensional structures are being developed.

For example, Patent Document 1 discloses a stack semiconductor device inwhich two semiconductor devices are stacked. Patent Document 1 alsodiscloses a technique of providing a buffer for adjusting the stress tobe caused by a through electrode. Further, Patent Document 2 discloses atechnique for reducing diffusion of copper (Cu) in a semiconductordevice by preventing the main conductor film made of copper (Cu) frombeing brought into contact with the upper surface (CMP surface) of aninsulating film.

CITATION LIST Patent Documents

Patent Document 1: Japanese Patent Application Laid-Open No. 2012-142414

Patent Document 2: Japanese Patent Application Laid-Open No. 2003-124311

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Meanwhile, in a solid-state imaging device as a semiconductor devicehaving a three-dimensional structure, if a pumping phenomenon (Cupumping) occurs due to the heat treatment after bonding when twosubstrates are stacked and bonded to each other, the wafer bondingbecome inadequate, and bonding defects might appear. Therefore, therehas been a demand for a technique for reducing bonding defects when twosubstrates are laminated and bonded to each other.

The present technology has been made in view of such circumstances, andaims to reduce bonding defects when two substrates are bonded to eachother.

Solutions to Problems

A solid-state imaging device according to one aspect of the presenttechnology is a solid-state imaging device that includes: a firstsubstrate including a first electrode formed with a metal; and a secondsubstrate that is a substrate bonded to the first substrate, the secondsubstrate including a second electrode formed with a metal, the secondelectrode being bonded to the first electrode. In at least one of thefirst substrate or the second substrate, a diffusion preventing layer ofthe metal is formed for a layer formed with the metal filling a holeportion, the metal forming the electrodes.

In the solid-state imaging device according to one aspect of the presenttechnology, the diffusion preventing layer of the metal is formed forthe layer in which the metal forming the electrodes is buried in thehole portion in at least one of the first substrate including the firstelectrode formed with a metal, or the second substrate that is thesubstrate bonded to the first substrate, the second substrate includingthe second electrode formed with the metal, the second electrode beingbonded to the first electrode.

A manufacturing method according to one aspect of the present technologyis a method for manufacturing a solid-state imaging device thatincludes: a first substrate including a first electrode formed with ametal; and a second substrate that is a substrate bonded to the firstsubstrate, the second substrate including a second electrode formed witha metal, the second electrode being bonded to the first electrode. Themethod includes: forming a first layer in which the metal is buried in afirst hole portion; forming a diffusion preventing layer of the metal,the diffusion preventing layer being stacked on the first layer; andforming a second layer in which the metal is buried in a second holeportion to form a connecting pad portion, the second layer being stackedon the first layer and the diffusion preventing layer, the first layer,the diffusion preventing layer, and the second layer being formed in atleast one of the first substrate or the second substrate.

In the manufacturing method according to one aspect of the presenttechnology, the first layer in which the metal is buried in the firsthole portion is formed, the diffusion preventing layer of the metal isformed so as to be stacked on the first layer, and the second layer inwhich the metal is buried in the second hole portion to form theconnecting pad portion is formed so as to be stacked on the first layerand the diffusion preventing layer. The first layer, the diffusionpreventing layer, and the second layer are formed in at least one of thefirst substrate including the first electrode formed with the metal, orthe second substrate bonded to the first substrate, the second substrateincluding the second electrode formed with the metal, the secondelectrode being bonded to the first electrode.

Effects of the Invention

According to one aspect of the present technology, bonding defects canbe reduced when two substrates are bonded to each other.

Note that the effects of the present technology are not limited to theeffect described herein, and may include any of the effects described inthe present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing the configuration of an embodiment of asolid-state imaging device to which the present technology is applied.

FIG. 2 is a cross-sectional diagram showing the state of the bondingportion when a pumping phenomenon occurs while two substrates are bondedto each other.

FIG. 3 is a cross-sectional view of relevant parts, showing thestructure of a solid-state imaging device according to a firstembodiment.

FIG. 4 is a diagram showing various example combinations of the uppersurface shape of the via of a first layer and the upper surface shape ofthe via of a second layer.

FIG. 5 is a diagram showing example sizes of the upper surface and thelower surface of the via in the second layer.

FIG. 6 is a table showing the results of comparisons among thestructures of A through C of FIG. 5.

FIG. 7 is a diagram showing the flow of a manufacturing process.

FIG. 8 is a diagram showing the flow of a manufacturing process.

FIG. 9 is a cross-sectional view of relevant parts, showing thestructure of a solid-state imaging device according to a secondembodiment.

FIG. 10 is a cross-sectional view of relevant parts, showing a firstspecific example of the structure of a solid-state imaging device towhich the present technology is applied.

FIG. 11 is a cross-sectional view of relevant parts, showing a secondspecific example of the structure of a solid-state imaging device towhich the present technology is applied.

FIG. 12 is a diagram showing an example configuration of an electronicapparatus using a solid-state imaging device to which the presenttechnology is applied.

FIG. 13 is a diagram showing examples of use of a solid-state imagingdevice to which the present technology is applied.

FIG. 14 is a block diagram schematically showing an exampleconfiguration of an in-vivo information acquisition system.

FIG. 15 is a diagram schematically showing an example configuration ofan endoscopic surgery system.

FIG. 16 is a block diagram showing an example of the functionalconfigurations of a camera head and a CCU.

FIG. 17 is a block diagram schematically showing an exampleconfiguration of a vehicle control system.

FIG. 18 is an explanatory diagram showing an example of installationpositions of external information detectors and imaging units.

MODE FOR CARRYING OUT THE INVENTION

The following is a description of embodiments of the present technology,with reference to the drawings. Note that explanation will be made inthe following order.

1. General Example Configuration of a Solid-State Imaging Device

2. First Embodiment

3. Second Embodiment

4. Specific Example Configurations of Solid-State Imaging Devices

5. Example Configuration of an Electronic Apparatus

6. Examples of Use of the Solid-State Imaging Device

7. Example Application to an In-Vivo Information Acquisition System

8. Example Application to an Endoscopic Surgery System

9. Example Applications to Moving Objects

1. General Example Configuration of a Solid-State Imaging Device

FIG. 1 is a diagram showing the configuration of an embodiment of asolid-state imaging device to which the present technology is applied.

In FIG. 1, a solid-state imaging device 1 is a semiconductor devicehaving a three-dimensional structure that includes a first substrate 11as a sensor substrate and a second substrate 21 as a circuit substratebonded to the first substrate 11 in a stacked state. This solid-stateimaging device 1 is designed as an image sensor, such as a complementarymetal oxide semiconductor (CMOS) image sensor, for example.

In the solid-state imaging device 1, the first substrate 11 has a pixelregion 13 in which a plurality of pixels 12 including photoelectricconversion units is two-dimensionally arranged in a regular pattern. Inthis pixel region 13, a plurality of pixel drive lines 14 is arranged inthe row direction, and a plurality of vertical signal lines 15 isarranged in the column direction, so that each pixel 12 is connected toone pixel drive line 14 and one vertical signal line 15.

Further, each pixel 12 includes a photoelectric conversion unit, afloating diffusion region (FD), and a pixel circuit formed with aplurality of pixel transistors and the like. Note that a plurality ofthe pixels 12 may share part of a pixel circuit in some cases.

On the other hand, peripheral circuits such as a vertical drive circuit22, a column signal processing circuit 23, a horizontal drive circuit24, and a system control circuit 25 are formed in the second substrate21.

While the solid-state imaging device 1 is formed with the firstsubstrate 11 and the second substrate 21 bonded to each other, it isknown that a so-called pumping phenomenon (Cu pumping) occurs during aheat treatment (annealing treatment) after bonding those substrates, andthe copper (Cu) used for the electrodes expands (bulges). Due to thelocal copper (Cu) bulging phenomenon caused by this heat treatment (ordue to plastic deformation caused by thermal stress), the wafer bondingstrength decreases, and the bonding becomes inadequate, which might leadto defective electrical connection or peeling.

(Bonding Portion at the Time of a Pumping Phenomenon)

FIG. 2 is a cross-sectional diagram showing the state of the bondingportion between electrodes when a pumping phenomenon occurs while twosubstrates are bonded to each other.

As shown in A of FIG. 2, a laminated film 900-1 in which an interlayerinsulating film 901-1, a liner insulating film 902-1, and an interlayerinsulating film 903-1 are stacked is formed in the upper substrate ofthe two substrates to be bonded. A metallic film 905-1 made of copper(Cu) is formed as an electrode in the laminated film 900-1. Note that ametal seed film 904-1 is formed between the laminated film 900-1 and themetallic film 905-1.

Meanwhile, in the lower substrate, copper (Cu) as a metallic film 905-2is formed in a laminated film 900-2 in which an interlayer insulatingfilm 901-2 through an interlayer insulating film 903-2 are stacked, in asimilar manner as in the upper substrate.

B of FIG. 2 shows the structure of the bonding portion between the twosubstrates after bonding. Then, a heat treatment is then performed inthe state of the bonding portion shown in B of FIG. 2, so that thebonding portion enters a state shown in C of FIG. 2. That is, the heattreatment causes a pumping phenomenon, and the copper (Cu) as themetallic films 905-1 and 905-2 formed in the laminated films 900-1 and900-2 of the upper and lower substrates expands (910-1 and 910-2 in thedrawing).

As described above, when such a pumping phenomenon occurs, the waferbonding strength decreases, and the bonding becomes inadequate, whichmight lead to defective electrical bonding. In view of the above, thepresent technology suggests a solution for reducing the bonding defects,to enable reduction of defects in the electrode bonding when twosubstrates are bonded to each other.

In the description below, such solutions will be described withreference to two embodiments: a first embodiment and a secondembodiment.

2. First Embodiment

(Structure of the Bonding Portion)

FIG. 3 is a cross-sectional view of relevant parts, showing thestructure of a solid-state imaging device 1 according to the firstembodiment. In the description below, the configuration of thesolid-state imaging device 1 according to the first embodiment isspecifically described, with reference to the cross-sectional view ofthe relevant parts.

Note that, of the first substrate 11 and the second substrate 21 bondedin the solid-state imaging device 1, the second substrate 21 will bedescribed as a typical example with reference to FIG. 3, but the firstsubstrate 11 may have a similar structure (the structure of the firstembodiment). Further, the surface on the upper side in the drawing is abonding surface 21S of the second substrate 21 or a bonding surface 11Sof the first substrate 11.

In FIG. 3, a laminated film 100 in which a first layer 100-1 and asecond layer 100-2 are stacked is formed in the second substrate 21.

The first layer 100-1 includes an interlayer insulating film 101 made ofsilicon oxide (SiO₂) or the like. Note that the coefficient of thermalexpansion (CTE) of silicon oxide (SiO₂) is 0.5×10⁻⁶/K.

In the first layer 100-1, a via 111 as a first hole portion is formed inthe interlayer insulating film 101, and a metallic film 105-1 is buriedtherein. Note that, in the case explained in the description below,copper (Cu) is used as the metallic film 105-1. Copper (Cu) has acoefficient of thermal expansion of 16.5×10⁻⁶/K.

Further, in the first layer 100-1, a metal seed film 104-1 as a barriermetal is formed between the side surface of the via 111 and the metallicfilm 105-1. The metal seed film 104-1 may be a film formed with tantalum(Ta), titanium (Ti), or the like, for example. Note that the coefficientof thermal expansion of tantalum (Ta) is 6.3×10⁻⁶/K. Further, thecoefficient of thermal expansion of titanium (Ti) is 8.6×10⁻⁶/K.

Meanwhile, the second layer 100-2 stacked as the upper layer on thefirst layer 100-1 as the lower layer includes an interlayer insulatingfilm 103 made of silicon oxide (SiO₂) or the like. In the second layer100-2, a via 112 as a second hole portion is formed in the interlayerinsulating film 103, and a metallic film 105-2 made of copper (Cu) isburied therein.

That is, in the second layer 100-2, the metallic film 105-2 is buried inthe via 112, so that a pad portion 121 made of copper (Cu) is formed onthe side of the bonding surface 21S. Note that, in the second layer100-2, a metal seed film 104-2 made of tantalum (Ta), titanium (Ti), orthe like is also formed between the side surface of the via 112 and themetallic film 105-2.

Here, in the laminated film 100, a diffusion preventing layer 100-3 isformed between the first layer 100-1 and the second layer 100-2.

The diffusion preventing layer 100-3 includes a diffusion preventingfilm 102. The diffusion preventing film 102 is an insulating film, andis a film formed with a silicon compound such as silicon nitride (SiN),silicon carbonitride (SiCN), or silicon carbide (SiC), for example. Notethat the coefficient of thermal expansion of silicon nitride (SiN) is2.8×10⁻⁶/K. Further, the coefficient of thermal expansion of siliconcarbide (SiC) is 3.7×10⁻⁶/K.

The diffusion preventing film 102 is formed under the interlayerinsulating film 103 of the second layer 100-2 as the upper layer (underthe region excluding the metal seed film 104-2 and the metallic film105-2 formed in the via 112), so as to be in contact with the metal seedfilm 104-1 formed on the side surface of the via 111 of the first layer100-1 as the lower layer and part of the metallic film 105-1.

Note that, in the first layer 100-1, a hard mask 106 is formed on theinterlayer insulating film 101, and is in contact with the diffusionpreventing film 102 of the diffusion preventing layer 100-3. However,the hard mask 106 is not necessarily formed.

Further, the metal seed film 104-2 is formed not only between the sidesurface of the via 112 and the metallic film 105-2, but also in theregion under the metallic film 105-2. That is, the metal seed film 104-2is also formed between the metallic film 105-2 buried in the via 112 ofthe second layer 100-2 and the metallic film 105-1 buried in the via 111of the first layer 100-1, and forms part of the diffusion preventinglayer 100-3.

As described above, in the second substrate 21, the diffusion preventinglayer 100-3 including the diffusion preventing film 102 and part of themetal seed film 104-2 is formed between the first layer 100-1 and thesecond layer 100-2, and functions as a “support” that reduces volumeexpansion of the copper (Cu) serving as the metallic film 105-1 buriedin the via 111 of the first layer 100-1 as the lower layer.

Then, the diffusion preventing layer 100-3 then reduces thermalexpansion of the metallic film 105-1 of copper (Cu) during the heattreatment after the bonding of the bonding surfaces (11S and 21S) of thefirst substrate 11 and the second substrate 21. As a result, it becomespossible to prevent a copper (Cu) pumping phenomenon (Cu pumping) fromoccurring in the bonding surface 21S (or the bonding surface 11S).

Further, as such a structure is adopted, the total volume of the copper(Cu) used as the metallic films 105-1 and 105-2 can also be reduced.That is, in contrast to the structure of the laminated film 900-1 or thelaminated film 900-2 shown in FIG. 2 described above, for example, thediffusion preventing film 102 is formed so that the diameter of the via112 of the second layer 100-2 is smaller than the diameter of the via111 of the first layer 100-1 in the structure of the laminated film 100shown in FIG. 3. As a result, the total volume of the copper (Cu) can bemade smaller.

Note that, in FIG. 3, the prevention of a pumping phenomenon isindicated by four arrows in the drawing. That is, in FIG. 3, the twoarrows pointing to the upper side from the lower side in the drawingindicate thermal expansion of the copper (Cu) serving as the metallicfilm 105-1 buried in the via 111 of the first layer 100-1. On the otherhand, the two arrows that face those arrows and point to the lower sidefrom the upper side in the drawing indicate that (the diffusionpreventing film 102 of) the diffusion preventing layer 100-3 reducesthermal expansion of the copper (Cu) serving as the metallic film 105-1.

As described above, in the structure of the solid-state imaging device 1according to the first embodiment, the diffusion preventing layer 100-3is formed between the first layer 100-1 and the second layer 100-2, sothat copper (Cu) bonding defects due to thermal expansion of the copper(Cu) during the heat treatment after the bonding can be reduced.

Particularly, in a case where the substrates to be stacked are connectedby a through silicon electrode (through silicon via: TSV), the via ofthe through silicon electrode (TSV) has a great diameter and a greatdepth. Accordingly, the volume of the copper (Cu) buried therein islarge. For example, in the above described structure shown in FIG. 2 (aCu wiring structure in which a wiring layer and a connecting hole layerare connected), the volume of the copper (Cu) becomes larger during theheat treatment after the bonding. Therefore, the amount of bulging atthe time of a temperature rise becomes larger. As a result, bonding thepad portions (Cu—Cu bonding) becomes difficult.

In the structure of the present technology shown in FIG. 3, on the otherhand, a “support” that restricts movement of the copper (Cu) buried inthe lower layer is formed between the upper wiring layer (the secondlayer 100-2) and the lower connecting hole layer (the first layer100-1), or the total volume of the copper (Cu) is reduced. Thus, it ispossible to reduce copper (Cu) bonding defects due to thermal expansionof the copper (Cu) during the heat treatment after the bonding.

Note that, although the structure of the second substrate 21 has beendescribed herein as mentioned above, the first substrate 11 can have asimilar structure to reduce copper (Cu) bonding defects due to thermalexpansion. Then, the first substrate 11 and the second substrate 21 arethen bonded to each other, so that a through silicon electrode (TSV) isformed in the first substrate 11 and the second substrate 21, which havebeen stacked. At that point of time, the pad portions can be bonded(Cu—Cu bonding) with precision.

However, the structure shown in FIG. 3 can be adopted in at least onesubstrate between the first substrate 11 and the second substrate 21.Even in a case where the structure shown in FIG. 3 is adopted only ineither the first substrate 11 or the second substrate 21, copper (Cu)bonding defects due to thermal expansion can be reduced in at least oneof the substrates.

Note that, in the structure shown in FIG. 3, the diffusion preventinglayer 100-3 includes part of the metal seed film 104-2, but the metalseed film 104-2 is not necessarily included therein.

(Various Example Combinations of Upper Surface Shapes of the Vias)

FIG. 4 is a diagram showing various example combinations of the uppersurface shape of the via 111 of the first layer 100-1 and the uppersurface shape of the via 112 of the second layer 100-2. Note that FIG. 4shows the upper surface shapes of the vias in a case where the firstlayer 100-1 and the second layer 100-2 are viewed from the bondingsurface 21S (or the bonding surface 11S) (or in a plan view).

Here, example combinations of the upper surface shape of the via 111formed in the first layer 100-1 and the upper surface shape of the via112 formed in the second layer 100-2 are shown in A through D of FIG. 4.

In A of FIG. 4, the upper surface of the via 111 formed in the firstlayer 100-1 has a square shape. On the other hand, the upper surface ofthe via 112 formed in the second layer 100-2 has a circular shape.Accordingly, the connecting pad portion 121 also has a circular shape.Here, the area of the upper surface of the via 112 (the area of acircle) is smaller than the area of the upper surface of the via 111(the area of a square).

In B of FIG. 4, the upper surface of the via 111 formed in the firstlayer 100-1 has a square shape. Meanwhile, the shape of the pad portion121 on the upper surface of the via 112 formed in the second layer 100-2also has a square shape. Here, the area of the upper surface of the via112 (the area of a square) is smaller than the area of the upper surfaceof the via 111 (the area of a square).

In C of FIG. 4, the upper surface of the via 111 formed in the firstlayer 100-1 has a circular shape. Meanwhile, the shape of the padportion 121 on the upper surface of the via 112 formed in the secondlayer 100-2 also has a circular shape. Here, the area of the uppersurface of the via 112 (the area of a circle) is smaller than the areaof the upper surface of the via 111 (the area of a circle).

In D of FIG. 4, the upper surface of the via 111 formed in the firstlayer 100-1 has a circular shape. Meanwhile, the shape of the padportion 121 on the upper surface of the via 112 formed in the secondlayer 100-2 has a square shape. Here, the area of the upper surface ofthe via 112 (the area of a square) is smaller than the area of the uppersurface of the via 111 (the area of a circle).

As described above, various combinations of shapes can be adopted as thecombination of the upper surface shape of the via 111 formed in thefirst layer 100-1 and the upper surface shape of the via 112 formed inthe second layer 100-2. However, the diameter of the via 112 in thesecond layer 100-2 is smaller than the diameter of the via 111 in thefirst layer 100-1.

In other words, a result of comparison between the sizes of the longestportions of the upper surface shape of the via 111 and the upper surfaceshape of the via 112 shows that the Cu wiring line on the upper surfaceof the via 111 is longer than the Cu wiring line on the upper surface ofthe via 112.

Note that the combinations of shapes shown in FIG. 4 are merelyexamples, and any shape pattern that can be generated during thephotolithography process may be adopted. That is, the diameter of thevia 111 in the first layer 100-1 and the diameter of the via 112 in thesecond layer 100-2 may be the same or may be different.

(Example Sizes of the Upper Surface and the Lower Surface of the Via inthe Second Layer)

FIG. 5 shows example sizes of the upper surface and the lower surface ofthe via 112 in the second layer 100-2. Note that FIG. 5 showscross-sectional structures of laminated films 100 each including a firstlayer 100-1, a second layer 100-2, and a diffusion preventing layer100-3.

Here, examples sizes of the upper surface and the lower surface(dimensions of the upper and lower portions) of the via 112 in thesecond layer 100-2 are shown in A through C of FIG. 5. However, in Athrough C of FIG. 5, the size of the upper surface (the bonding surface)(the dimension of the upper portion) of the via 112 is fixed at aconstant value (arrows pointing to the right and the left in thedrawing), and the size of the lower surface (the surface on the oppositeside from the bonding surface) (the dimension of the lower portion) ofthe via 112 is variable. Comparisons are made in cases where the size ofthe lower surface of the via 112 is varied.

In A of FIG. 5, the upper surface and the lower surface of the via 112formed in the second layer 100-2 have the same size. Here, the twoarrows pointing to the upper side from the lower side in the drawingindicate thermal expansion of the copper (Cu) serving as the metallicfilm 105-1 buried in the via 111 of the first layer 100-1. On the otherhand, the two arrows that face those arrows and point to the lower sidefrom the upper side in the drawing indicate that (the diffusionpreventing film 102 of) the diffusion preventing layer 100-3 reducesthermal expansion of the copper (Cu) serving as the metallic film 105-1.

In B of FIG. 5, the size of the lower surface of the via 112 formed inthe second layer 100-2 is smaller than the size of the upper surfacethereof. In this case, as indicated by the arrows in the drawing, thearrows that face the two arrows indicating thermal expansion of thecopper (Cu) (the arrows pointing to the upper side from the lower sidein the drawing) are larger than the arrows shown in A of FIG. 5.

This is because, in the structure in B of FIG. 5, the size of the lowersurface of the via 112 is smaller, so that the region of the diffusionpreventing film 102 can be larger (can protrude more greatly) withrespect to the metallic film 105-1 accordingly. Therefore, it is safe tosay that the structure in B of FIG. 5 is a structure superior to thestructure in A of FIG. 5 in reducing thermal expansion of the copper(Cu) serving as the metallic film 105-1.

In C of FIG. 5, the size of the lower surface of the via 112 formed inthe second layer 100-2 is larger than the size of the upper surfacethereof. In this case, as indicated by the arrows in the drawing, thearrows that face the two arrows indicating thermal expansion of thecopper (Cu) (the arrows pointing to the upper side from the lower sidein the drawing) are smaller than the arrows shown in A of FIG. 5.

This is because, in the structure in C of FIG. 5, the size of the lowersurface of the via 112 is larger, so that the region of the diffusionpreventing film 102 can be narrower with respect to the metallic film105-1 accordingly. Therefore, it is safe to say that the structure in Cof FIG. 5 is a structure inferior to the structure in A of FIG. 5 inreducing thermal expansion of the copper (Cu) serving as the metallicfilm 105-1.

The above facts can be summarized as shown in FIG. 6, for example. Thatis, FIG. 6 shows the results of comparisons among the structures shownin A through C of FIG. 5: the top row shows the results of comparisonsof the volume of the copper (Cu) serving as the metallic film 105-2buried in the via 112 formed in the second layer 100-2 as the upperlayer; and the bottom row shows the results of comparisons of the effectto reduce thermal expansion of the copper (Cu) serving as the metallicfilm 105-1 buried in the via 111 formed in the first layer 100-1 as thelower layer.

As shown in the top row in FIG. 6, the volume of the copper (Cu) in theupper layer is the smallest in the structure shown in B of FIG. 5, andis the second smallest in the structure shown in A of FIG. 5. Further,the volume of the copper (Cu) in the upper layer is the largest in thestructure shown in C of FIG. 5.

Furthermore, as shown in the bottom row in FIG. 6, the effect to reducethermal expansion of the copper (Cu) in the lower layer is the greatestin the structure shown in B of FIG. 5, and is the second greatest in thestructure shown in A of FIG. 5. Further, the effect to reduce thermalexpansion of the copper (Cu) in the lower layer is the smallest in thestructure shown in C of FIG. 5.

From these comparison results, the diameter of the via 112 is madesmaller in the surface on the opposite side from the bonding surfacethan in the bonding surface in the second layer 100-2, so that theregion of the diffusion preventing film 102 can be made wider (canprotrude more greatly) with respect to the metallic film 105-1. As sucha structure shown in B of FIG. 5 is adopted, the effects of the presenttechnology can be further enhanced.

Note that, in the first substrate 11 and the second substrate 21 thatare bonded to each other in the solid-state imaging device 1 of thefirst embodiment, the region corresponding to the above describedbonding portion shown in FIG. 3 is a particular peripheral region of theregion surrounding the pixel region 13 in the first substrate 11, forexample. That is, FIG. 3 shows the bonding portion between theperipheral region of the pixel region 13 in the first substrate 11 andthe region corresponding to the peripheral region in the secondsubstrate 21, for example.

Further, as a process according to a method for manufacturing thesolid-state imaging device 1 of the first embodiment, the processillustrated in FIGS. 7 and 8 is performed on at least one substratebetween the first substrate 11 and the second substrate 21, for example.Note that, although not shown in the drawings, the diffusion preventinglayer 100-3 and the second layer 100-2 are stacked on the first layer100-1 prior to the process illustrated in FIGS. 7 and 8 in thismanufacturing process.

That is, after the metal seed film 104-1 is formed in the via 111 formedin the interlayer insulating film 101, the metallic film 105-1 made ofcopper (Cu) is buried in the via 111, to form the first layer 100-1.Further, the diffusion preventing film 102 and the interlayer insulatingfilm 103 are stacked on the first layer 100-1 (A of FIG. 7).

After that, as shown in B of FIG. 7, a photolithography process isperformed, and a photoresist 311 is applied onto the interlayerinsulating film 103, to generate a resist pattern for forming the via112 (patterning). As shown in C of FIG. 7, an etching process is thenperformed, and dry etching is performed, with the mask being the resistpattern generated in the photolithography process. As a result, the via112 is formed in the diffusion preventing film 102 and the interlayerinsulating film 103.

Next, as shown in D of FIG. 7, an asking/cleaning process is performed,so that the resist film of the photoresist 311 is removed, and wetcleaning is performed. As shown in E of FIG. 8, a first metallic filmforming process is then performed, so that the metal seed film 104-2 isformed on the upper layer of the interlayer insulating film 103 and inthe via 112 by sputtering.

Next, as shown in F of FIG. 8, a second metallic film forming process isperformed, so that a Cu seed layer is formed by sputtering, and themetallic film 105-2 made of copper (Cu) is further buried in the via 112by Cu plating. Then, as shown in G of FIG. 8, a polishing/planarizingprocess is then performed, so that the excess portion of the metallicfilm 105-2 and the metal seed film 104-2 on the interlayer insulatingfilm 103 are removed by CMP (Chemical Mechanical Planarization).

As the above process is performed, the structure of the first substrate11 or the second substrate 21 shown in FIG. 3 and the like can beformed.

3. Second Embodiment

(Structure of the Bonding Portion)

FIG. 9 is a cross-sectional view of relevant parts, showing thestructure of a solid-state imaging device according to a secondembodiment. In the description below, the configuration of a solid-stateimaging device 1 according to the second embodiment is specificallydescribed, with reference to the cross-sectional view of the relevantparts.

Note that, of a first substrate 11 and a second substrate 21 bonded inthe solid-state imaging device 1, the second substrate 21 will bedescribed as a typical example with reference to FIG. 9, but the firstsubstrate 11 may have a similar structure (the structure of the secondembodiment).

In FIG. 9, a laminated film 200 in which a first layer 200-1 and asecond layer 200-2 are stacked is formed in the second substrate 21.

In the first layer 200-1, a via 211 is formed in an interlayerinsulating film 201 made of silicon oxide (SiO₂) or the like, and ametallic film 205-1 made of copper (Cu) is buried therein. Note that, inthe first layer 200-1, a hard mask 206 is formed on the interlayerinsulating film 201.

Further, a metal seed film 204-1 as a barrier metal is formed betweenthe side surface of the via 211 and the metallic film 205-1. The metalseed film 204-1 may be a film formed with tantalum (Ta), titanium (Ti),or the like, for example.

On the other hand, in the second layer 200-2, a via 212 is formed in aninterlayer insulating film 203 made of silicon oxide (SiO₂) or the like,and a metallic film 205-2 made of copper (Cu) is buried therein. In thesecond layer 200-2, the metallic film 205-2 is buried in the via 212, sothat a pad portion 221 made of copper (Cu) is formed on the side of thebonding surface 21S.

In the second layer 200-2, a metal seed film 204-2 is also formedbetween the side surface of the via 212 and the metallic film 205-2. Themetal seed film 204-2 may be a film using tantalum (Ta), tantalumnitride (TaN), titanium (Ti), titanium nitride (TiN), tungsten (W),tungsten nitride (WN), a cobalt (Co)-containing alloy, manganese oxide(MnO), molybdenum (Mo), ruthenium (Ru), or the like, for example.

Here, in the laminated film 200, a diffusion preventing layer 200-3 isformed between the first layer 200-1 and the second layer 200-2. Thediffusion preventing layer 200-3 includes part of the metal seed film204-2.

That is, the metal seed film 204-2 is formed not only between the sidesurface of the via 212 and the metallic film 205-2, but also in theregion under the metallic film 205-2. Accordingly, the metal seed film204-2 is also formed between the metallic film 205-2 buried in the via212 of the second layer 200-2 and the metallic film 205-1 buried in thevia 211 of the first layer 200-1, and forms the diffusion preventinglayer 100-3.

As described above, in the second substrate 21, the diffusion preventinglayer 200-3 including part of the metal seed film 204-2 is formedbetween the first layer 200-1 and the second layer 200-2, and functionsas a “support” that reduces volume expansion of the copper (Cu) servingas the metallic film 205-1 buried in the via 211 of the first layer200-1 as the lower layer. Thus, it is also possible to reduce thermalexpansion of the metallic film 205-1 made of copper (Cu) during the heattreatment after bonding the bonding surfaces (11S and 21S) of the firstsubstrate 11 and the second substrate 21.

Note that, although a solid-state imaging device to which the presenttechnology is applied has been described above as an example, thepresent technology can be applied not only to a solid-state imagingdevice but also to any semiconductor device in which substrates arebonded and stacked.

4. Specific Example Configurations of Solid-State Imaging Devices

FIG. 10 is a cross-sectional view of relevant parts, showing a firstspecific example of the structure of a solid-state imaging device towhich the present technology is applied.

In FIG. 10, the first substrate 11 includes a semiconductor layer 411made of silicon turned into a thin film. The pixel region 13 in which aplurality of pixels formed with photodiodes (PDs) to serve asphotoelectric conversion units and a plurality of pixel transistors aretwo-dimensionally arranged in a regular manner is formed in thesemiconductor layer 411.

In the first substrate 11, a wiring layer 412 is formed on the frontsurface side of the semiconductor layer 411, and a light blocking filmis formed on the back surface side of the semiconductor layer 411including the upper portion of an optical black region 451. Colorfilters (CFs) and on-chip lenses (OCLs) are further formed an effectivepixel region 452.

Also, in FIG. 10, a logic circuit 461 forming a peripheral circuit isformed in a predetermined region of a semiconductor layer 421 made ofsilicon in the second substrate 21. In the second substrate 21, a wiringlayer 422 is formed on the front surface side of the semiconductor layer421.

In the first substrate 11 and the second substrate 21 having the abovedescribed structure, the bonding surface 11S of the first substrate 11and the bonding surface 21S of the second substrate 21 are bonded toeach other, and (the structure of a portion in the vicinity of thebonding surface of) at least one layer of the wiring layer 412 of thefirst substrate 11 and the wiring layer 422 of the second substrate 21has the structure corresponding to the laminated film 100 shown in FIG.3 (including the diffusion preventing layer 100-3).

With this arrangement, thermal expansion of the metallic film (copper(Cu)) during the heat treatment after the bonding of the bondingsurfaces (11S and 21S) of the first substrate 11 and the secondsubstrate 21 can be reduced. As a result, it becomes possible to preventa copper (Cu) pumping phenomenon (Cu pumping) from occurring in thebonding surface 11S of the bonding surface 21S.

FIG. 11 is a cross-sectional view of relevant parts, showing a secondspecific example of the structure of a solid-state imaging device towhich the present technology is applied.

In FIG. 11, the first substrate 11 includes a semiconductor layer 511,and a pixel region in which a plurality of pixels formed withphotodiodes (PDs) and a plurality of pixel transistors aretwo-dimensionally arranged in a regular manner is formed in thesemiconductor layer 511. In the first substrate 11, a wiring layer 512is formed on the front surface side of the semiconductor layer 511, andcolor filters (CFs) and on-chip lenses (OCLs) are formed above therespective photodiodes (PDs) on the back surface side of thesemiconductor layer 511.

Also, in FIG. 11, a peripheral circuit is formed in a predeterminedregion of a semiconductor layer 521 in the second substrate 21. In thesecond substrate 21, a wiring layer 522 is formed on the front surfaceside of the semiconductor layer 521.

In the first substrate 11 and the second substrate 21 having the abovedescribed structure, the bonding surface 11S and the bonding surface 21Sare bonded to each other, and (the structure of a portion in thevicinity of the bonding surface of) at least one layer of the wiringlayer 512 of the first substrate 11 and the wiring layer 522 of thesecond substrate 21 has the structure corresponding to the laminatedfilm 100 shown in FIG. 3 (including the diffusion preventing layer100-3). Thus, it is possible to prevent a copper (Cu) pumping phenomenon(Cu pumping) from occurring in the bonding surface 11S or the bondingsurface 21S during the heat treatment.

5. Example Configuration of an Electronic Apparatus

The above described solid-state imaging device 1 as a semiconductordevice can be applied to a camera system such as a digital camera or avideo camera, for example, and can be further applied to an electronicapparatus such as a portable telephone having an imaging function orsome other device having an imaging function.

FIG. 12 is a diagram showing an example configuration of an electronicapparatus using a solid-state imaging device to which the presenttechnology is applied. FIG. 12 shows, as an example of such anelectronic apparatus, an example configuration of an imaging apparatus1000 as a video camera capable of capturing a still image or a movingimage.

In FIG. 12, the imaging apparatus 1000 includes: a solid-state imagingdevice 1001; an optical system 1002 that guides incident light to alight receiving sensor unit of the solid-state imaging device 1001; ashutter device 1003; a drive circuit 1004 that drives the solid-stateimaging device 1001; and a signal processing circuit 1005 that processesan output signal of the solid-state imaging device 1001.

The above described solid-state imaging device 1 (FIG. 1) is used as thesolid-state imaging device 1001. The optical system (an optical lens)1002 gathers image light (incident light) from an object, and forms animage on the imaging surface of the solid-state imaging device 1001.With this, signal charges are stored in the solid-state imaging device1001 for a certain period of time. Such an optical system 1002 may be anoptical lens system including a plurality of optical lenses.

The shutter device 1003 controls the light exposure period and the lightblocking period for the solid-state imaging device 1001. The drivecircuit 1004 supplies a drive signal to the solid-state imaging device1001 and the shutter device 1003. With the supplied drive signal (atiming signal), the drive circuit 1004 controls an operation to beperformed by the solid-state imaging device 1001 to output a signal tothe signal processing circuit 1005, and controls a shutter operation ofthe shutter device 1003. That is, by supplying the drive signal (timingsignal), the drive circuit 1004 performs an operation to be performed bythe solid-state imaging device 1001 to transfer a signal to the signalprocessing circuit 1005.

The signal processing circuit 1005 performs various kinds of signalprocessing on signals transferred from the solid-state imaging device1001. A video signal obtained by this signal processing is stored into astorage medium such as a memory in a later stage, or is output to amonitor, for example.

In the electronic apparatus using a solid-state imaging device to whichthe present technology described above is applied, the solid-stateimaging device 1 capable of reducing electrode bonding defects when twosubstrates are stacked and bonded to each other can be used as thesolid-state imaging device 1001.

6. Examples of Use of a Solid-State Imaging Device

FIG. 13 is a diagram showing examples of use of a solid-state imagingdevice to which the present technology is applied.

The solid-state imaging device 1 can be used in various cases wherelight such as visible light, infrared light, ultraviolet light, or anX-ray is sensed, as described below, for example. That is, as shown inFIG. 13, the solid-state imaging device 1 can be employed in anapparatus that is used not only in the appreciation activity field whereimages are taken and are used in appreciation activities, but also inthe field of transportation, the field of home electric appliances, thefields of medicine and healthcare, the field of security, the field ofbeauty care, the field of sports, or the field of agriculture, forexample.

Specifically, in the appreciation activity field, the solid-stateimaging device 1 can be used in an apparatus (the imaging apparatus 1000in FIG. 12, for example) for capturing images to be used in appreciationactivities, such as a digital camera, a smartphone, or a portabletelephone with a camera function, as described above.

In the field of transportation, the solid-state imaging device 1 can beused in apparatuses for transportation use, such as vehicle-mountedsensors configured to capture images of the front, the back, thesurroundings, the inside of an automobile, and the like to perform safedriving such as an automatic stop and recognize a driver's condition orthe like, surveillance cameras for monitoring running vehicles androads, and ranging sensors or the like for measuring distances betweenvehicles, for example.

In the field of home electric appliances, the solid-state imaging device1 can be used in an apparatus to be used as home electric appliances,such as a television set, a refrigerator, or an air conditioner, tocapture images of gestures of users and operate the apparatus inaccordance with the gestures, for example. Also, in the fields ofmedicine and healthcare, the solid-state imaging device 1 can be used inan apparatus for medical use or healthcare use, such as an endoscope oran apparatus for receiving infrared light for angiography, for example.

In the field of security, the solid-state imaging device 1 can be usedin apparatuses for security use, such as surveillance cameras for crimeprevention and cameras for personal authentication, for example.Further, in the field of beauty care, the solid-state imaging device 1can be used in an apparatus for beauty care use, such as a skinmeasurement apparatus configured to image the skin or a microscope forimaging the scalp, for example.

In the field of sports, the solid-state imaging device 1 can be used inapparatuses for sporting use, such as action cameras and wearablecameras for sports, for example. Further, in the field of agriculture,the solid-state imaging device 1 can be used in apparatuses foragricultural use, such as cameras for monitoring conditions of fieldsand crops, for example.

7. Example Application to an In-Vivo Information Acquisition System

The technology (the present technology) according to the presentdisclosure can be applied to various products. For example, thetechnology according to the present disclosure may be applied to anendoscopic surgery system.

FIG. 14 is a block diagram schematically showing an exampleconfiguration of a patient's in-vivo information acquisition systemusing a capsule endoscope to which the technology (the presenttechnology) according to the present disclosure may be applied.

An in-vivo information acquisition system 10001 includes a capsuleendoscope 10100 and an external control device 10200.

The capsule endoscope 10100 is swallowed by the patient at the time ofexamination. The capsule endoscope 10100 has an imaging function and awireless communication function. Before naturally discharged from thepatient, the capsule endoscope 10100 moves inside the internal organssuch as the stomach and the intestines by peristaltic motion or thelike, sequentially captures images of the inside of the internal organs(these images will be hereinafter also referred to as in-vivo images) atpredetermined intervals, and sequentially transmits information aboutthe in-vivo images to the external control device 10200 outside the bodyin a wireless manner.

Further, the external control device 10200 controls the overalloperation of the in-vivo information acquisition system 10001. Theexternal control device 10200 also receives the information about thein-vivo images transmitted from the capsule endoscope 10100, and, on thebasis of the received in-vivo image information, generates image datafor displaying the in-vivo images on a display device (not shown).

In this manner, the in-vivo information acquisition system 10001 canacquire in-vivo images showing the states of the inside of the body ofthe patient at any appropriate time until the swallowed capsuleendoscope 10100 is discharged.

The configurations and the functions of the capsule endoscope 10100 andthe external control device 10200 are now described in greater detail.

The capsule endoscope 10100 has a capsule-like housing 10101, and thehousing 10101 houses a light source unit 10111, an imaging unit 10112,an image processing unit 10113, a wireless communication unit 10114, apower feeder unit 10115, a power supply unit 10116, and a control unit10117.

The light source unit 10111 is formed with a light source such as alight emitting diode (LED), for example, and emits light onto theimaging field of view of the imaging unit 10112.

The imaging unit 10112 is formed with an imaging device and an opticalsystem including a plurality of lenses provided in front of the imagingdevice. Reflected light of light emitted to body tissue as the currentobservation target (this reflected light will be hereinafter referred toas the observation light) is collected by the optical system, and entersthe imaging device. In the imaging unit 10112, the observation lightincident on the imaging device is photoelectrically converted, and animage signal corresponding to the observation light is generated. Theimage signal generated by the imaging unit 10112 is supplied to theimage processing unit 10113.

The image processing unit 10113 is formed with a processor such as acentral processing unit (CPU) or a graphics processing unit (GPU), andperforms various kinds of signal processing on the image signalgenerated by the imaging unit 10112. The image processing unit 10113supplies the image signal subjected to the signal processing as RAW datato the wireless communication unit 10114.

Further, the wireless communication unit 10114 performs predeterminedprocessing such as modulation processing on the image signal subjectedto the signal processing by the image processing unit 10113, andtransmits the image signal to the external control device 10200 via anantenna 10114A. The wireless communication unit 10114 also receives acontrol signal related to control of driving of the capsule endoscope10100 from the external control device 10200 via the antenna 10114A. Thewireless communication unit 10114 supplies the control signal receivedfrom the external control device 10200 to the control unit 10117.

The power feeder unit 10115 includes an antenna coil for powerreception, a power regeneration circuit that regenerates electric powerfrom the current generated in the antenna coil, a booster circuit, andthe like. In the power feeder unit 10115, electric power is generatedaccording to a so-called non-contact charging principle.

The power supply unit 10116 is formed with a secondary battery, andstores the electric power generated by the power feeder unit 10115. InFIG. 14, to avoid complication of the drawing, an arrow or the likeindicating the destination of power supply from the power supply unit10116 is not shown. However, the electric power stored in the powersupply unit 10116 is supplied to the light source unit 10111, theimaging unit 10112, the image processing unit 10113, the wirelesscommunication unit 10114, and the control unit 10117, and can be usedfor driving these units.

The control unit 10117 is formed with a processor such as a CPU, anddrives the light source unit 10111, the imaging unit 10112, the imageprocessing unit 10113, the wireless communication unit 10114, and thepower feeder unit 10115 unit as appropriate in accordance with a controlsignal transmitted from the external control device 10200.

The external control device 10200 is formed with a processor such as aCPU or a GPU, or a microcomputer, a control board, or the like on whicha processor and a storage element such as a memory are mounted together.The external control device 10200 controls operation of the capsuleendoscope 10100 by transmitting a control signal to the control unit10117 of the capsule endoscope 10100 via an antenna 10200A. In thecapsule endoscope 10100, the conditions for emitting light to thecurrent observation target in the light source unit 10111 can be changedin accordance with the control signal from the external control device10200, for example. Further, the imaging conditions (such as the framerate and the exposure value in the imaging unit 10112, for example) canalso be changed in accordance with the control signal from the externalcontrol device 10200. Further, the contents of the processing in theimage processing unit 10113 and the conditions (such as the transmissionintervals and the number of images to be transmitted, for example) forthe wireless communication unit 10114 to transmit image signals may bechanged in accordance with the control signal from the external controldevice 10200.

Further, the external control device 10200 also performs various kindsof image processing on the image signal transmitted from the capsuleendoscope 10100, and generates image data for displaying a capturedin-vivo image on the display device. Examples of the image processinginclude various kinds of signal processing, such as a developmentprocess (a demosaicing process), an image quality enhancement process (aband emphasizing process, a super-resolution process, a noise reduction(NR) process, a camera shake correction process, and/or the like),and/or an enlargement process (an electronic zooming process), forexample. The external control device 10200 controls driving of thedisplay device, to cause the display device to display an in-vivo imagecaptured on the basis of the generated image data. Alternatively, theexternal control device 10200 may cause a recording device (not shown)to record the generated image data, or cause a printing device (notshown) to print out the generated image data.

An example of an in-vivo information acquisition system to which thetechnology according to the present disclosure can be applied has beendescribed above. The technology according to the present disclosure canbe applied to the imaging unit 10112 in the above describedconfiguration. Specifically, the solid-state imaging device 1 in FIG. 1can be applied to the imaging unit 10112. With this solid-state imagingdevice 1, it is possible to reduce defects in electrode bonding whenstacking and bonding two substrates.

8. Example Application to an Endoscopic Surgery System

The technology (the present technology) according to the presentdisclosure can be applied to various products. For example, thetechnology according to the present disclosure may be applied to anendoscopic surgery system.

FIG. 15 is a diagram schematically showing an example configuration ofan endoscopic surgery system to which the technology (the presenttechnology) according to the present disclosure may be applied.

FIG. 15 shows a situation where a surgeon (a physician) 11131 isperforming surgery on a patient 11132 on a patient bed 11133, using anendoscopic surgery system 11000. As shown in the drawing, the endoscopicsurgery system 11000 includes an endoscope 11100, other surgical tools11110 such as a pneumoperitoneum tube 11111 and an energy treatment tool11112, a support arm device 11120 that supports the endoscope 11100, anda cart 11200 on which various kinds of devices for endoscopic surgeryare mounted.

The endoscope 11100 includes a lens barrel 11101 that has a region of apredetermined length from the top end to be inserted into a body cavityof the patient 11132, and a camera head 11102 connected to the base endof the lens barrel 11101. In the example shown in the drawing, theendoscope 11100 is configured as a so-called rigid scope having a rigidlens barrel 11101. However, the endoscope 11100 may be configured as aso-called flexible scope having a flexible lens barrel.

At the top end of the lens barrel 11101, an opening into which anobjective lens is inserted is provided. A light source device 11203 isconnected to the endoscope 11100, and the light generated by the lightsource device 11203 is guided to the top end of the lens barrel by alight guide extending inside the lens barrel 11101, and is emittedtoward the current observation target in the body cavity of the patient11132 via the objective lens. Note that the endoscope 11100 may be aforward-viewing endoscope, an oblique-viewing endoscope, or aside-viewing endoscope.

An optical system and an imaging device are provided inside the camerahead 11102, and reflected light (observation light) from the currentobservation target is converged on the imaging device by the opticalsystem. The observation light is photoelectrically converted by theimaging device, and an electrical signal corresponding to theobservation light, or an image signal corresponding to the observationimage, is generated. The image signal is transmitted as RAW data to acamera control unit (CCU) 11201.

The CCU 11201 is formed with a central processing unit (CPU), a graphicsprocessing unit (GPU), or the like, and collectively controls operationsof the endoscope 11100 and a display device 11202. Further, the CCU11201 receives an image signal from the camera head 11102, and subjectsthe image signal to various kinds of image processing, such as adevelopment process (demosaicing process), for example, to display animage based on the image signal.

Under the control of the CCU 11201, the display device 11202 displays animage based on the image signal subjected to the image processing by theCCU 11201.

The light source device 11203 is formed with a light source such as alight emitting diode (LED), for example, and supplies the endoscope11100 with illuminating light for imaging the surgical site or the like.

An input device 11204 is an input interface to the endoscopic surgerysystem 11000. The user can input various kinds of information andinstructions to the endoscopic surgery system 11000 via the input device11204. For example, the user inputs an instruction or the like to changeimaging conditions (such as the type of illuminating light, themagnification, and the focal length) for the endoscope 11100.

A treatment tool control device 11205 controls driving of the energytreatment tool 11112 for tissue cauterization, incision, blood vesselsealing, or the like. A pneumoperitoneum device 11206 injects a gas intoa body cavity of the patient 11132 via the pneumoperitoneum tube 11111to inflate the body cavity, for the purpose of securing the field ofview of the endoscope 11100 and the working space of the surgeon. Arecorder 11207 is a device capable of recording various kinds ofinformation about the surgery. A printer 11208 is a device capable ofprinting various kinds of information relating to the surgery in variousformats such as text, images, graphics, and the like.

Note that the light source device 11203 that supplies the endoscope11100 with the illuminating light for imaging the surgical site can beformed with an LED, a laser light source, or a white light source thatis a combination of an LED and a laser light source, for example. In acase where a white light source is formed with a combination of RGBlaser light sources, the output intensity and the output timing of eachcolor (each wavelength) can be controlled with high precision.Accordingly, the white balance of an image captured by the light sourcedevice 11203 can be adjusted. Alternatively, in this case, laser lightfrom each of the RGB laser light sources may be emitted onto the currentobservation target in a time-division manner, and driving of the imagingdevice of the camera head 11102 may be controlled in synchronizationwith the timing of the light emission. Thus, images corresponding to therespective RGB colors can be captured in a time-division manner.According to the method, a color image can be obtained without any colorfilter provided in the imaging device.

Further, the driving of the light source device 11203 may also becontrolled so that the intensity of light to be output is changed atpredetermined time intervals. The driving of the imaging device of thecamera head 11102 is controlled in synchronism with the timing of thechange in the intensity of the light, and images are acquired in atime-division manner and are then combined. Thus, a high dynamic rangeimage with no black portions and no white spots can be generated.

Further, the light source device 11203 may also be designed to becapable of supplying light of a predetermined wavelength band compatiblewith special light observation. In special light observation, light of anarrower band than the illuminating light (or white light) at the timeof normal observation is emitted, with the wavelength dependence oflight absorption in body tissue being taken advantage of, for example.As a result, so-called narrow band imaging is performed to imagepredetermined tissue such as a blood vessel in a mucosal surface layeror the like, with high contrast. Alternatively, in the special lightobservation, fluorescence observation for obtaining an image withfluorescence generated through emission of excitation light may beperformed. In fluorescence observation, excitation light is emitted tobody tissue so that the fluorescence from the body tissue can beobserved (autofluorescence observation). Alternatively, a reagent suchas indocyanine green (ICG) is locally injected into body tissue, andexcitation light corresponding to the fluorescence wavelength of thereagent is emitted to the body tissue so that a fluorescent image can beobtained, for example. The light source device 11203 can be designed tobe capable of suppling narrowband light and/or excitation lightcompatible with such special light observation.

FIG. 16 is a block diagram showing an example of the functionalconfigurations of the camera head 11102 and the CCU 11201 shown in FIG.15.

The camera head 11102 includes a lens unit 11401, an imaging unit 11402,a drive unit 11403, a communication unit 11404, and a camera headcontrol unit 11405. The CCU 11201 includes a communication unit 11411,an image processing unit 11412, and a control unit 11413. The camerahead 11102 and the CCU 11201 are communicably connected to each other bya transmission cable 11400.

The lens unit 11401 is an optical system provided at the connectingportion with the lens barrel 11101. Observation light captured from thetop end of the lens barrel 11101 is guided to the camera head 11102, andenters the lens unit 11401. The lens unit 11401 is formed with acombination of a plurality of lenses including a zoom lens and a focuslens.

The imaging unit 11402 is formed with an imaging device. The imagingunit 11402 may be formed with one imaging device (a so-calledsingle-plate type), or may be formed with a plurality of imaging devices(a so-called multiple-plate type). In a case where the imaging unit11402 is of a multiple-plate type, for example, image signalscorresponding to the respective RGB colors may be generated by therespective imaging devices, and be then combined to obtain a colorimage. Alternatively, the imaging unit 11402 may be designed to includea pair of imaging devices for acquiring right-eye and left-eye imagesignals compatible with three-dimensional (3D) display. As the 3Ddisplay is conducted, the surgeon 11131 can grasp more accurately thedepth of the body tissue at the surgical site. Note that, in a casewhere the imaging unit 11402 is of a multiple-plate type, a plurality oflens units 11401 are provided for the respective imaging devices.

Further, the imaging unit 11402 is not necessarily provided in thecamera head 11102. For example, the imaging unit 11402 may be providedimmediately behind the objective lens in the lens barrel 11101.

The drive unit 11403 is formed with an actuator, and, under the controlof the camera head control unit 11405, moves the zoom lens and the focuslens of the lens unit 11401 by a predetermined distance along theoptical axis. With this arrangement, the magnification and the focalpoint of the image captured by the imaging unit 11402 can beappropriately adjusted.

The communication unit 11404 is formed with a communication device fortransmitting and receiving various kinds of information to and from theCCU 11201. The communication unit 11404 transmits the image signalobtained as RAW data from the imaging unit 11402 to the CCU 11201 viathe transmission cable 11400.

Further, the communication unit 11404 also receives a control signal forcontrolling the driving of the camera head 11102 from the CCU 11201, andsupplies the control signal to the camera head control unit 11405. Thecontrol signal includes information about imaging conditions, such asinformation for specifying the frame rate of captured images,information for specifying the exposure value at the time of imaging,and/or information for specifying the magnification and the focal pointof captured images, for example.

Note that the above imaging conditions such as the frame rate, theexposure value, the magnification, and the focal point may beappropriately specified by the user, or may be automatically set by thecontrol unit 11413 of the CCU 11201 on the basis of an acquired imagesignal. In the latter case, the endoscope 11100 has a so-calledauto-exposure (AE) function, an auto-focus (AF) function, and anauto-white-balance (AWB) function.

The camera head control unit 11405 controls the driving of the camerahead 11102, on the basis of a control signal received from the CCU 11201via the communication unit 11404.

The communication unit 11411 is formed with a communication device fortransmitting and receiving various kinds of information to and from thecamera head 11102. The communication unit 11411 receives an image signaltransmitted from the camera head 11102 via the transmission cable 11400.

Further, the communication unit 11411 also transmits a control signalfor controlling the driving of the camera head 11102, to the camera head11102. The image signal and the control signal can be transmittedthrough electrical communication, optical communication, or the like.

The image processing unit 11412 performs various kinds of imageprocessing on an image signal that is RAW data transmitted from thecamera head 11102.

The control unit 11413 performs various kinds of control relating todisplay of an image of the surgical portion or the like captured by theendoscope 11100, and a captured image obtained through imaging of thesurgical site or the like. For example, the control unit 11413 generatesa control signal for controlling the driving of the camera head 11102.

Further, the control unit 11413 also causes the display device 11202 todisplay a captured image showing the surgical site or the like, on thebasis of the image signal subjected to the image processing by the imageprocessing unit 11412. In doing so, the control unit 11413 may recognizethe respective objects shown in the captured image, using various imagerecognition techniques. For example, the control unit 11413 can detectthe shape, the color, and the like of the edges of an object shown inthe captured image, to recognize the surgical tool such as forceps, aspecific body site, bleeding, the mist at the time of use of the energytreatment tool 11112, and the like. When causing the display device11202 to display the captured image, the control unit 11413 may causethe display device 11202 to superimpose various kinds of surgery aidinformation on the image of the surgical site on the display, using therecognition result. As the surgery aid information is superimposed anddisplayed, and thus, is presented to the surgeon 11131, it becomespossible to reduce the burden on the surgeon 11131, and enable thesurgeon 11131 to proceed with the surgery in a reliable manner.

The transmission cable 11400 connecting the camera head 11102 and theCCU 11201 is an electrical signal cable compatible with electric signalcommunication, an optical fiber compatible with optical communication,or a composite cable thereof.

Here, in the example shown in the drawing, communication is performed ina wired manner using the transmission cable 11400. However,communication between the camera head 11102 and the CCU 11201 may beperformed in a wireless manner.

An example of an endoscopic surgery system to which the techniqueaccording to the present disclosure can be applied has been describedabove. The technology according to the present disclosure can be appliedto the imaging unit 11402 of the camera head 11102. Specifically, thesolid-state imaging device 1 in FIG. 1 can be applied to the imagingunit 11402. With this solid-state imaging device 1, it is possible toreduce defects in electrode bonding when stacking and bonding twosubstrates.

9. Example Applications to Moving Objects

The technology (the present technology) according to the presentdisclosure can be applied to various products. For example, thetechnology according to the present disclosure may be embodied as anapparatus mounted on any type of moving object, such as an automobile,an electrical vehicle, a hybrid electrical vehicle, a motorcycle, abicycle, a personal mobility device, an airplane, a drone, a vessel, ora robot.

FIG. 17 is a block diagram schematically showing an exampleconfiguration of a vehicle control system that is an example of a movingobject control system to which the technology according to the presentdisclosure may be applied.

The vehicle control system 12000 includes a plurality of electroniccontrol units connected via a communication network 12001. In theexample shown in FIG. 17, the vehicle control system 12000 includes adrive system control unit 12010, a body system control unit 12020, anexternal information detection unit 12030, an in-vehicle informationdetection unit 12040, and an overall control unit 12050. Further, amicrocomputer 12051, a sound/image output unit 12052, and an in-vehiclenetwork interface (I/F) 12053 are also shown as the functionalcomponents of the overall control unit 12050.

The drive system control unit 12010 controls operations of the devicesrelated to the drive system of the vehicle according to variousprograms. For example, the drive system control unit 12010 functions ascontrol devices such as a driving force generation device for generatinga driving force of the vehicle such as an internal combustion engine ora driving motor, a driving force transmission mechanism for transmittingthe driving force to the wheels, a steering mechanism for adjusting thesteering angle of the vehicle, and a braking device for generating abraking force of the vehicle.

The body system control unit 12020 controls operations of the variousdevices mounted on the vehicle body according to various programs. Forexample, the body system control unit 12020 functions as a keyless entrysystem, a smart key system, a power window device, or a control devicefor various lamps such as a headlamp, a backup lamp, a brake lamp, aturn signal lamp, a fog lamp, or the like. In this case, the body systemcontrol unit 12020 can receive radio waves transmitted from a portabledevice that substitutes for a key, or signals from various switches. Thebody system control unit 12020 receives inputs of these radio waves orsignals, and controls the door lock device, the power window device, thelamps, and the like of the vehicle.

The external information detection unit 12030 detects informationoutside the vehicle equipped with the vehicle control system 12000. Forexample, an imaging unit 12031 is connected to the external informationdetection unit 12030. The external information detection unit 12030causes the imaging unit 12031 to capture an image of the outside of thevehicle, and receives the captured image. On the basis of the receivedimage, the external information detection unit 12030 may perform anobject detection process for detecting a person, a vehicle, an obstacle,a sign, characters on the road surface, or the like, or perform adistance detection process.

The imaging unit 12031 is an optical sensor that receives light, andoutputs an electrical signal corresponding to the amount of receivedlight. The imaging unit 12031 can output an electrical signal as animage, or output an electrical signal as distance measurementinformation. Further, the light to be received by the imaging unit 12031may be visible light, or may be invisible light such as infrared rays.

The in-vehicle information detection unit 12040 detects informationabout the inside of the vehicle. For example, a driver state detector12041 that detects the state of the driver is connected to thein-vehicle information detection unit 12040. The driver state detector12041 includes a camera that captures an image of the driver, forexample, and, on the basis of detected information input from the driverstate detector 12041, the in-vehicle information detection unit 12040may calculate the degree of fatigue or the degree of concentration ofthe driver, or determine whether the driver is dozing off.

On the basis of the external/internal information acquired by theexternal information detection unit 12030 or the in-vehicle informationdetection unit 12040, the microcomputer 12051 can calculate the controltarget value of the driving force generation device, the steeringmechanism, or the braking device, and output a control command to thedrive system control unit 12010. For example, the microcomputer 12051can perform cooperative control to achieve the functions of an advanceddriver assistance system (ADAS), including vehicle collision avoidanceor impact mitigation, follow-up running based on the distance betweenvehicles, vehicle speed maintenance running, vehicle collision warning,vehicle lane deviation warning, or the like.

Further, the microcomputer 12051 can also perform cooperative control toconduct automatic driving or the like for autonomously running notdepending on the operation of the driver, by controlling the drivingforce generation device, the steering mechanism, the braking device, orthe like on the basis of information about the surroundings of thevehicle, the information having being acquired by the externalinformation detection unit 12030 or the in-vehicle information detectionunit 12040.

Further, the microcomputer 12051 can also output a control command tothe body system control unit 12020, on the basis of the externalinformation acquired by the external information detection unit 12030.For example, the microcomputer 12051 controls the headlamp in accordancewith the position of the leading vehicle or the oncoming vehicledetected by the external information detection unit 12030, and performscooperative control to achieve an anti-glare effect by switching from ahigh beam to a low beam, or the like.

The sound/image output unit 12052 transmits an audio output signaland/or an image output signal to an output device that is capable ofvisually or audibly notifying the passenger(s) of the vehicle or theoutside of the vehicle of information. In the example shown in FIG. 17,an audio speaker 12061, a display unit 12062, and an instrument panel12063 are shown as output devices. The display unit 12062 may include anon-board display and/or a head-up display, for example.

FIG. 18 is a diagram showing an example of installation positions ofimaging units 12031.

In FIG. 18, a vehicle 12100 includes imaging units 12101, 12102, 12103,12104, and 12105 as the imaging units 12031.

Imaging units 12101, 12102, 12103, 12104, and 12105 are provided at thefollowing positions: the front end edge of a vehicle 12100, a sidemirror, the rear bumper, a rear door, an upper portion, and the like ofthe front windshield inside the vehicle, for example. The imaging unit12101 provided on the front end edge and the imaging unit 12105 providedon the upper portion of the front windshield inside the vehicle mainlycapture images ahead of the vehicle 12100. The imaging units 12102 and12103 provided on the side mirrors mainly capture images on the sides ofthe vehicle 12100. The imaging unit 12104 provided on the rear bumper ora rear door mainly captures images behind the vehicle 12100. The frontimages acquired by the imaging units 12101 and 12105 are mainly used fordetection of a vehicle running in front of the vehicle 12100, apedestrian, an obstacle, a traffic signal, a traffic sign, a lane, orthe like.

Note that FIG. 18 shows an example of the imaging ranges of the imagingunits 12101 through 12104. An imaging range 12111 indicates the imagingrange of the imaging unit 12101 provided on the front end edge, imagingranges 12112 and 12113 indicate the imaging ranges of the imaging units12102 and 12103 provided on the respective side mirrors, and an imagingrange 12114 indicates the imaging range of the imaging unit 12104provided on the rear bumper or a rear door. For example, image datacaptured by the imaging units 12101 through 12104 are superimposed onone another, so that an overhead image of the vehicle 12100 viewed fromabove is obtained.

At least one of the imaging units 12101 through 12104 may have afunction of acquiring distance information. For example, at least one ofthe imaging units 12101 through 12104 may be a stereo camera including aplurality of imaging devices, or may be an imaging device having pixelsfor phase difference detection.

For example, in accordance with distance information obtained from theimaging units 12101 through 12104, the microcomputer 12051 calculatesthe distances to the respective three-dimensional objects within theimaging ranges 12111 through 12114, and temporal changes in thedistances (the speeds relative to the vehicle 12100). In this manner,the three-dimensional object that is the closest three-dimensionalobject on the traveling path of the vehicle 12100 and is traveling at apredetermined speed (0 km/h or higher, for example) in substantially thesame direction as the vehicle 12100 can be extracted as the vehiclerunning in front of the vehicle 12100. Further, the microcomputer 12051can set beforehand an inter-vehicle distance to be maintained in frontof the vehicle running in front of the vehicle 12100, and can performautomatic brake control (including follow-up stop control), automaticacceleration control (including follow-up start control), and the like.In this manner, it is possible to perform cooperative control to conductautomatic driving or the like to autonomously travel not depending onthe operation of the driver.

For example, in accordance with the distance information obtained fromthe imaging units 12101 through 12104, the microcomputer 12051 canextract three-dimensional object data concerning three-dimensionalobjects under the categories of two-wheeled vehicles, regular vehicles,large vehicles, pedestrians, utility poles, and the like, and use thethree-dimensional object data in automatically avoiding obstacles. Forexample, the microcomputer 12051 classifies the obstacles in thevicinity of the vehicle 12100 into obstacles visible to the driver ofthe vehicle 12100 and obstacles difficult to visually recognize. Then,the microcomputer 12051 then determines collision risks indicating therisks of collision with the respective obstacles. If a collision risk isequal to or higher than a set value, and there is a possibility ofcollision, the microcomputer 12051 can output a warning to the drivervia the audio speaker 12061 and the display unit 12062, or can performdriving support for avoiding collision by performing forced decelerationor avoiding steering via the drive system control unit 12010.

At least one of the imaging units 12101 through 12104 may be an infraredcamera that detects infrared rays. For example, the microcomputer 12051can recognize a pedestrian by determining whether or not a pedestrianexists in images captured by the imaging units 12101 through 12104. Suchpedestrian recognition is carried out through a process of extractingfeature points from the images captured by the imaging units 12101through 12104 serving as infrared cameras, and a process of performing apattern matching on the series of feature points indicating the outlinesof objects and determining whether or not there is a pedestrian, forexample. If the microcomputer 12051 determines that a pedestrian existsin the images captured by the imaging units 12101 through 12104, andrecognizes a pedestrian, the sound/image output unit 12052 controls thedisplay unit 12062 to display a rectangular contour line for emphasizingthe recognized pedestrian in a superimposed manner. Further, thesound/image output unit 12052 may also control the display unit 12062 todisplay an icon or the like indicating the pedestrian at a desiredposition.

An example of a vehicle control system to which the technology accordingto the present disclosure can be applied has been described above. Thetechnology according to the present disclosure can be applied to theimaging unit 12031 in the above described configuration. Specifically,the solid-state imaging device 1 in FIG. 1 can be applied to the imagingunit 12031. With this solid-state imaging device 1, it is possible toreduce defects in electrode bonding when stacking and bonding twosubstrates.

Note that the present technology may also be embodied in theconfigurations described below.

(1)

A solid-state imaging device including:

a first substrate including a first electrode formed with a metal; and

a second substrate that is a substrate bonded to the first substrate,the second substrate including a second electrode formed with a metal,the second electrode being bonded to the first electrode,

in which, in at least one of the first substrate or the secondsubstrate, a diffusion preventing layer of the metal is formed for alayer formed with the metal filling a hole portion, the metal formingthe electrodes.

(2)

The solid-state imaging device according to (1), in which

the diffusion preventing layer includes a diffusion preventing filmformed between a first layer in which the metal is buried in a firsthole portion, and a second layer in which the metal is buried in asecond hole portion to form a connecting pad portion.

(3)

The solid-state imaging device according to (1) or (2), in which

the diffusion preventing layer includes a metal seed film formed betweena first layer in which the metal is buried in a first hole portion, anda second layer in which the metal is buried in a second hole portion toform a connecting pad portion.

(4)

The solid-state imaging device according to (3), in which

the metal seed film is also formed between a side surface of the firsthole portion and the metal, and between a side surface of the secondhole portion and the metal.

(5)

The solid-state imaging device according to any one of (2) to (4), inwhich

a diameter of the second hole portion in the second layer is smallerthan a diameter of the first hole portion in the first layer.

(6)

The solid-state imaging device according to (5), in which

the diameter of the first hole portion and the diameter of the secondhole portion have the same shape or different shapes.

(7)

The solid-state imaging device according to any one of (2) to (6), inwhich,

in the second layer, a diameter of the second hole portion is smaller ina surface on the opposite side from a bonding surface than in thebonding surface.

(8)

The solid-state imaging device according to (2), in which the diffusionpreventing film is an insulating film.

(9)

The solid-state imaging device according to (8), in which

the insulating film is a film using silicon nitride (SiN), siliconcarbonitride (SiCN), or silicon carbide (SiC).

(10)

The solid-state imaging device according to (3) or (4), in which

the metal seed film is a film using tantalum (Ta) or titanium (Ti).

(11)

The solid-state imaging device according to any one of (1) to (10), inwhich

the metal forming the first electrode and the second electrode is copper(Cu).

(12)

The solid-state imaging device according to any one of (1) to (11), inwhich

the diffusion preventing layer is a layer for preventing diffusion ofthe metal at a time of heat treatment after bonding of bonding surfacesof the first substrate and the second substrate.

(13)

The solid-state imaging device according to any one of (1) to (12), inwhich

the first substrate is a sensor substrate having a pixel region in whicha plurality of pixels including a photoelectric conversion unit aretwo-dimensionally arranged, and

the second substrate is a circuit substrate including a predeterminedcircuit.

(14)

A method for manufacturing a solid-state imaging device that includes:

a first substrate including a first electrode formed with a metal; and

a second substrate that is a substrate bonded to the first substrate,the second substrate including a second electrode formed with a metal,the second electrode being bonded to the first electrode,

the method including:

forming a first layer in which the metal is buried in a first holeportion;

forming a diffusion preventing layer of the metal, the diffusionpreventing layer being stacked on the first layer; and

forming a second layer in which the metal is buried in a second holeportion to form a connecting pad portion, the second layer being stackedon the first layer and the diffusion preventing layer,

the first layer, the diffusion preventing layer, and the second layerbeing formed in at least one of the first substrate or the secondsubstrate.

REFERENCE SIGNS LIST

-   1 Solid-state imaging device-   11 First substrate-   11S Bonding surface-   12 Pixel-   13 Pixel region-   14 Pixel drive line-   15 Vertical signal line-   21 Second substrate-   21S Bonding surface-   22 Vertical drive circuit-   23 Column signal processing circuit-   24 Horizontal drive circuit-   25 System control circuit-   100 Laminated film-   100-1 First layer-   100-2 Second layer-   100-3 Diffusion preventing layer-   101 Interlayer insulating film-   102 Diffusion preventing film-   103 Interlayer insulating film-   104-1, 104-2 Metal seed film-   105-1, 105-2 Metallic film-   111 Via-   112 Via-   121 Pad portion-   1000 Imaging apparatus-   1001 Solid-state imaging device-   10112 Imaging unit-   12031 Imaging unit

1. A solid-state imaging device comprising: a first substrate includinga first electrode formed with a metal; and a second substrate that is asubstrate bonded to the first substrate, the second substrate includinga second electrode formed with a metal, the second electrode beingbonded to the first electrode, wherein, in at least one of the firstsubstrate or the second substrate, a diffusion preventing layer of themetal is formed for a layer formed with the metal filling a holeportion, the metal forming the electrodes.
 2. The solid-state imagingdevice according to claim 1, wherein the diffusion preventing layerincludes a diffusion preventing film formed between a first layer inwhich the metal is buried in a first hole portion, and a second layer inwhich the metal is buried in a second hole portion to form a connectingpad portion.
 3. The solid-state imaging device according to claim 2,wherein the diffusion preventing layer includes a metal seed film formedbetween the first layer and the second layer.
 4. The solid-state imagingdevice according to claim 3, wherein the metal seed film is also formedbetween a side surface of the first hole portion and the metal, andbetween a side surface of the second hole portion and the metal.
 5. Thesolid-state imaging device according to claim 2, wherein a diameter ofthe second hole portion in the second layer is smaller than a diameterof the first hole portion in the first layer.
 6. The solid-state imagingdevice according to claim 5, wherein the diameter of the first holeportion and the diameter of the second hole portion have the same shapeor different shapes.
 7. The solid-state imaging device according toclaim 2, wherein, in the second layer, a diameter of the second holeportion is smaller in a surface on the opposite side from a bondingsurface than in the bonding surface.
 8. The solid-state imaging deviceaccording to claim 2, wherein the diffusion preventing film is aninsulating film.
 9. The solid-state imaging device according to claim 8,wherein the insulating film is a film using silicon nitride (SiN),silicon carbonitride (SiCN), or silicon carbide (SiC).
 10. Thesolid-state imaging device according to claim 4, wherein the metal seedfilm is a film using tantalum (Ta) or titanium (Ti).
 11. The solid-stateimaging device according to claim 1, wherein the metal forming the firstelectrode and the second electrode is copper (Cu).
 12. The solid-stateimaging device according to claim 1, wherein the diffusion preventinglayer is a layer for preventing diffusion of the metal at a time of heattreatment after bonding of bonding surfaces of the first substrate andthe second substrate.
 13. The solid-state imaging device according toclaim 1, wherein the first substrate is a sensor substrate having apixel region in which a plurality of pixels including a photoelectricconversion unit are two-dimensionally arranged, and the second substrateis a circuit substrate including a predetermined circuit.
 14. A methodfor manufacturing a solid-state imaging device that includes: a firstsubstrate including a first electrode formed with a metal; and a secondsubstrate that is a substrate bonded to the first substrate, the secondsubstrate including a second electrode formed with a metal, the secondelectrode being bonded to the first electrode, the method comprising:forming a first layer in which the metal is buried in a first holeportion; forming a diffusion preventing layer of the metal, thediffusion preventing layer being stacked on the first layer; and forminga second layer in which the metal is buried in a second hole portion toform a connecting pad portion, the second layer being stacked on thefirst layer and the diffusion preventing layer, the first layer, thediffusion preventing layer, and the second layer being formed in atleast one of the first substrate or the second substrate.